Portion of a motorcycle swing arm



FIG. 1 is a side view of the portion of a motorcycle swing arm, shown in position of use from the left side of the motorcycle; and,

FIG. 2 is an enlarged side perspective view of the portion of a motorcycle swing arm.

The broken line showing of the environment is for illustrative purposes only and forms no part of the claimed design. 

We claim the ornamental design for a portion of a motorcycle swing arm, as shown and described. 